Retail stores have incorporated beacon technology into stores in recent years in order to communicate with customers in ways previously not possible. Through use of beaconing technology, localized promotional advertising to customers within the retail stores is possible. For example, a retailer who wants to promote children's shoes to shoppers near a shoe section of a retail store can broadcast a promotional message to portable devices, such as smartphones, of shoppers when the shoppers come within a certain range of a fixed-position broadcast beacon or beacon anchor. One example of beacon technology is the iBeacon™ produced by Apple Inc.
Currently, technology used for beaconing is implemented using Bluetooth® low-energy (BLE) devices and protocol stacks. The BLE devices and protocol stacks have several drawbacks, including ranging data being based only on a received signal strength indication (RSSI) measurement that has low stability and is severely affected by the environment, “clutter” (or unwanted echo signals), and other noise-producing parameters, which results in range measurement inaccuracy. The RSSI measurement is used to determine a distance zone at which a portable device is located from the beacon, where the zones are defined as immediate (a few centimeters), near (a few meters), and far (approximately 10 meters).
As a result of RSSI having low stability, a condition in which “hot zone” indications are unstable and lead to false positives or alarms is created. The RSSI measurement is critical because signal strength decreases rapidly. As understood in the art, signal strength decreases with a square of the distance, and, in this case, between the beacon anchor and mobile device. Moreover, the presence of structures and otherwise, such as shelves, floor, people walking within a field of an antenna, and other items in stores and other indoor environments, creates “clutter” or echo signals, which makes it even more difficult to distinguish a primary beacon signal from signal bounces and reflections that affect the primary BLE beacon signal. Such alteration in signal strength reduces accuracy of location estimates as the RSSI measurement is generally lower as a result of the “clutter,” and, thus, the beacon anchor appears to be farther from a portable device measuring the signal strength.
Another problem that results from the use of BLE devices within retail stores is the inability to determine relative position of a portable device from a beacon anchor. Antennas used with BLE devices typically broadcast a generally symmetric antenna pattern around the beacon anchor, which means that a portable device that measures the beacon signal in front of the beacon anchor typically has the same RSSI measurement as a portable device that measures the beacon signal behind the beacon anchor. As a result, false positives result when a portable device is behind the beacon anchor. Accordingly, there is a need to improve accuracy and to reduce false alarms for indoor locating systems.